DETECTOR AND DETECTION METHOD FOR METALLIC FOREIGN MATTER

PROBLEM TO BE SOLVED: To detect metallic foreign matter of smaller sizes than before without being affected by noise while dispensing with forming any Lissajous figure, as to a detector for metallic foreign matter mixedly existing in powder of nonconductive material. SOLUTION: A magnetizer M comprises a yoke Y and a coil C. A body 4 under inspection of powder is moved on a conveyor 3 between magnetic poles P1 and P2 of the magnetizer M. When metallic foreign matter exists mixedly in the body 4, an eddy current is induced in the foreign matter by magnetic flux generated by the coil C to generate Joule heat. An infrared camera 21 converts infrared rays radiated from the body 4 into an electric signal. A photographing signal of the camera 21 is sent via a photographing control circuit 22 to a monitor 23 and to a foreign matter detection circuit 24. The detection circuit 24 makes a comparison with a photographing signal obtained when no metallic foreign matter mixedly exists, thereby determining whether or not metallic foreign matter exists. A foreign matter detection signal is generated when metallic foreign matter mixedly exists. COPYRIGHT: (C)2005,JPO&NCIPI